Pre-Cambrian Rocks of Ross-shire. 225 
lower gneiss rocks nearly in the positions in which they are now 
found, the present inclination of the beds being dependent upon 
subsequent movements, accompanied by some faults. These upper 
beds are undoubtedly made out of such materials as would be de- 
rived from rocks similar to those which now underlie them, and to 
which they are unconformable; and hence it is that sometimes a 
superficial examination may possibly lead one to associate them. 
The persistent and equal metamorphism, the contorted character, 
and high N.W. strike of the lower series is so marked, however, that 
for any distance it seems almost impossible to confound them in any 
way with the comparatively undisturbed and unequally altered beds 
of the upper series, which also almost invariably strike in the oppo- 
site direction, or from N.E. to 8.W., at a low angle of dip.” 
That these beds gradually assume a more horizontal position as 
we ascend the Glen eastwards is undoubted. The high dip given to 
them in the section by Murchison and Geikie! is certainly not war- 
ranted by examination, except for a short distance near the escarp- 
ment; nor indeed would it appear at all reasonable, for the thickness 
required under these circumstances would be enormous, especially as 
these beds are indicated by them in other sections along this line to 
underlie the rocks composing the great mountains to the east. In 
some of the sections given by these authors the conformable thick- 
ness shown is truly appalling, and, I need hardly say, physically 
impossible, when we take into consideration the conditions which 
must have prevailed over these areas when the sediments were 
deposited. If these rocks were to underlie those to the eastward as 
supposed, one would naturally ask at first what would be the 
amount of faulting necessary for so sudden a change, if, as most agree, 
the old floor is still traceable as far at least as the east side of Glen 
Laggan. Considering also that the conformable sequence shown in 
most of their sections” cannot be less than ten miles (in one at least 
twelve miles), and usually at a dip of from 40° to 50°, and that all the 
sediments must have been deposited horizontally, one is not only 
astounded at the faulting necessary, but beyond all at the physical 
conditions required to allow such an accumulation of sediments. It 
seems to me perfectly clear that no attempt could have been made to 
realize the physical difficulties necessary to uphold this theory before 
it was propounded. That these sections also should have been so 
frequently reproduced, not only to show the supposed succession 
along this line, but also in a more or less modified condition for other 
areas, is truly remarkable! 
These beds, according to my reading of the section, not only 
gradually assume a horizontal position, but terminate in the Glen 
which separates Craig Roy from Ben Fin; and instead of dipping 
under the latter mountain as supposed, overlie horizontally, or with 
a slight inclination only, the rocks near its foot, which form part of 
the Pre-Cambrian floor. 
1 Quart. Journ. Geol. Soe. vol. xvii. p. 191. 
2 Quart. Journ. Geol. Soc. vol. xv. p. 260; ibid. vol. xvii. p. 212; ‘ Siluria,”’ 
4th ed. pp. 169 and 172; and Sec. i. in Geol. Map of Scotland (Geikie), 1876. 
DECADE II.—VOL. VII.—NO. V. 15 
